MARINA DEL REY, Calif. — Thanks to a revolution in the recognition of head injuries and the consequences they can hold for athletes at every level, concussion denial seems to be on the way out.

"It's taken a long time to get there, but right now I think the public awareness is huge," Dr. Robert Cantu of the Neurologic Sports Injury Center at Boston's Brigham and Women's hospital said yesterday at the second National Sports Concussion Summit.

"It's as if the Berlin Wall of concussion denial has fallen," said sports agent Leigh Steinberg, noting a significant shift in both attitude and action within sports since the first summit was held a year ago.

Steinberg, who helped organize the summit along with the Sports Concussion Institute, is sponsoring a California program that will institute so-called "baseline testing" in 1,400 high schools, where athletes are given a cognitive exam that can be repeated after injuries to measure brain impairment.

Other smaller states like Hawai'i have introduced such testing, but the student athletes in California will represent the largest group ever to take the neurological exams, Steinberg said.

It's an attempt to remedy the inherent difficulty in measuring the effects of head injuries.

"It's a subjective diagnosis," Steinberg said. "You don't have a cast on your leg."

Similar neurological tests were made mandatory last year in the NFL, which was represented at this year's concussion summit after not appearing at the inaugural edition in 2007.

NFL medical officials said the things they institute in the "laboratory" that is their playing field are likely to appear at lower levels of sport.

"As often happens in the NFL there is a trickle-down phenomenon," said Dr. Elliott Pellman, the NFL's medical director.

The NFL also made official last year what had long been an unwritten rule, that players who lose consciousness during a game or practice must not return to the field that day.

Dr. Andrew Tucker, who was on the committee that formed the NFL's policy changes, said just as important were information sheets distributed to every NFL player in an attempt to prevent what he calls "unintentional underreporting," or players suffering concussions without recognizing any symptoms.

Other league changes include whistleblower provisions to confidentially report concussions and a booklet that will allow players and their families to identify symptoms.

"The commissioner is making a very strong statement that the safety of players takes precedence over competition," Tucker said.

The optimism expressed by many of yesterday's medical speakers was guarded, and renewed awareness of the problem has at times only led doctors to learn more about its severity.

Steinberg said it's gone from an "undiagnosed health epidemic" to an "under-diagnosed" health epidemic.

Studies have shown that in cases where athletes had three or more concussions, they were five times more at risk for early onset Alzheimer's disease, three times more at risk of significant memory loss and four times more likely to have severely elevated depression.